The present invention relates to active matrix displays, particularly to the formation of pixels for such displays, and more particularly, to a method for the formation of display pixels driven by silicon thin film transistors on plastic substrates.
In recent years substantial effort has been directed to the development of large area low cost electronics, such as flat panel displays, as well as portable electronics, and toys. Also, active matrix displays are being utilized in battlefield operations facilities, interior of ships, tanks and aircraft, as well as field-deployable portable electronics.
Conventional processing techniques used to fabricate active matrix liquid crystal displays (AMLCDs), for example, require processing temperatures of at least 300-350.degree. C. and as high as 600-650.degree. C. These high processing temperatures require that quartz or glass substrates be used for the active matrix pixel array, thereby eliminating the use of less expensive substrates such as various types of plastics. Recently, low-temperature processes have been developed to fabricate silicon thin film transistors (TFTs) on low-temperature plastic substrate materials, using substrates being incapable of withstanding processing temperatures greater than about 200.degree. C. These prior low-temperature processes are exemplified by copending U.S. application Ser. No. 08/611,318 filed Mar. 5, 1996, entitled "Method For Formation Of Thin Film Transistors On Plastic Substrates", assigned to the same assignee, and incorporated herein by reference thereto.
The present invention involves display pixels driven by silicon thin film transistors on low-temperature plastic substrates and a method for fabricating same. The method of this invention allows the fabrication of transistors on low-temperature plastic substrate materials, such as polyethyleneterephthalate (PET), which cannot withstand process temperatures in excess of 120.degree. C. The process of the present invention involves the integration of the low temperature silicon TFT process with the necessary operational steps to produce: 1) a pixel circuit containing the TFT and an optical element; and 2) an entire array of pixels.